1. Field of the Invention
The present invention relates to a steering device for a vehicle capable of adjusting a forward/rearward position of a steering wheel in accordance with a physical constitution of a driver.
2. Description of the Related Art
Japanese Patent Application Laid-open No. 2005-22450 discloses a steering device for a vehicle in which a steering wheel and a steering gear box are connected to each other via a steering shaft, a first universal joint, an intermediate shaft, a second universal joint and a pinion shaft, and a forward/rearward position of the steering wheel can be adjusted by constructing the intermediate shaft to be expandable and contractible and by supporting a steering column rotatably supporting the steering shaft at a vehicle body so as to be movable back and forth.
As shown in FIGS. 8A and 8B, in the conventional steering device for a vehicle, a steering wheel 11 is connected to a steering gear box via a steering shaft 12, a first universal joint 13, an intermediate shaft 14, a second universal joint 15 and a pinion shaft 16. Since the first and second universal joints 13 and 15 are constructed by non-constant velocity joints, the angular velocity of the steering shaft 12 and the angular velocity of the intermediate shaft 14 do not coincide with each other, and the angular velocity of the intermediate shaft 14 and the angular velocity of the pinion shaft 16 do not correspond to each other. Therefore, even if the steering shaft 12 (steering wheel 11) is rotated at a certain angular velocity, the pinion shaft 16 does not rotate at the certain angular velocity.
In order to rotate the steering shaft 12 and the pinion shaft 16 at equal angular velocity, the phase of a cross pin of the first universal joint 13 at a rear end of the intermediate shaft 14 and the phase of a cross pin of the second universal joint 15 at a front end of the intermediate shaft 14 are displaced by 90° from each other, and an inclination angle θ1 of the intermediate shaft 14 downward forward with respect to a forward extension line of the steering shaft 12, and an inclination angle θ2 of the pinion shaft 16 downward forward with respect to a forward extension line of the intermediate shaft 14 are made equal. This is because this arrangement cancels non-constant velocity of the first universal joint 13 and non-constant velocity of the second universal joint 15, and causes the steering shaft 12 and the pinion shaft 16 to rotate at the same angular velocity.
As shown by the chain lines in FIGS. 8A and 8B, even when the inclination angle θ1 of the intermediate shaft 14 downward forward with respect to the forward extension line of the steering 12, and the inclination angle θ2 of the pinion shaft 16 downward forward with respect to the forward extension line of the intermediate shaft 14 are set to be equal, if the intermediate shaft 14 is constructed to be expandable and contractible, and the steering shaft 12 is made adjustable in the forward/rearward position together with the steering wheel 11, the two inclination angles θ1′ and θ2′ (θ1″ and θ2″) do not coincide with each other with the forward/rearward movement of the steering shaft 12 as shown by the solid lines in FIGS. 8A and 8B, leading to a problem of losing constant velocity of the steering shaft 12 and the pinion shaft 16.